An important part of the manufacturing process is the testing of the manufactured products to determine if they satisfy predetermined specifications. Generally, the specifications provide a range of acceptable values, and for a product to pass the testing, the test results for the product should be within the range of acceptable values.
As background to a discussion of a specific class of products, it is well known that heat spontaneously flows from a high temperature heat source to a low temperature heat sink. However, when it is desired to reverse this spontaneous process and have heat transferred from a low temperature heat source to a high temperature heat sink, then a heat pump must be employed.
An electric refrigerator is a form of a heat pump. An electric refrigerator generally includes five basic parts: (1) the receiver; (2) the refrigerant-control device; (3) the evaporator; (4) the compressor; and (5) the condenser. The receiver serves as the low temperature heat source which is cooled by the electric refrigerator. The room in which the electric refrigerator is located serves as a high temperature heat sink. The evaporator is run at a lower temperature than the low temperature heat source (the inside of the receiver) and receives heat from the low temperature heat source, thereby cooling the inside of the receiver. The condenser is run at a higher temperature than the high temperature heat sink and transfers heat to the high temperature heat sink, the room in which the refrigerator is located.
Relevant tests relating to the performance of an electric refrigerator can be concerned with the ability of the electric refrigerator to pump adequate amounts of heat out from the low temperature heat source, for a specified range of heat loads in the low temperature heat source, to maintain the low temperature heat source in a desired temperature range. If the electric refrigerator can maintain the low temperature heat source in the desired temperature range for the specified range of heat loads, then the electric refrigerator is adequate. On the other hand, if the electric refrigerator can not maintain the low temperature heat source in the desired temperature range for the specified range of heat loads, then the electric refrigerator is inadequate.
With respect to the testing of refrigeration systems, existing technology dictates that the critical parameters of a refrigeration system be manually recorded at specific points in time in relationship to the testing cycle in order to determine performance characteristics. Due to a system's relatively low volumetric size, temperature changes occur very rapidly during the cool down and warm up cycles of a testing cycle. Inaccuracy in manual measurements can occur due to the occurrence of rapid temperature transitions as a result of a system's dynamics and size. Moreover, manual testing of multiple refrigeration systems undergoing similar testing cycles simultaneously is virtually impossible. By the time a manual tester has finished taking a measurement on a first refrigeration system, it may already be too late to take a comparable measurement in a second refrigeration system. Results for manual testing of third, fourth, etc. additional refrigeration systems would be much too late and highly inaccurate.
The ability to test multiple refrigeration systems simultaneously is very important. When multiple refrigeration systems are manufactured, if the multiple refrigeration systems cannot be tested rapidly and accurately, the entire manufacturing process is impeded. If numerous employees are assigned the task of testing, so that testing can be completed promptly and accurately, testing costs would be unacceptably high and therefor uneconomical.
It would therefore be desirable if a testing apparatus and method were provided for heat pumps in general, and refrigeration systems in particular, wherein critical parameters are tested automatically and under computer control. Moreover, it would be desirable if such a testing apparatus and method were provided in which multiple heat pumps, in general, and multiple refrigeration systems, in particular, can be tested simultaneously.